Using Zinc Cyanide as Sodium Cyanide Replacement

Q. Good Morning Fellow Platers.
We run a plating shop and are busy doing additions to our solutions, we realized that we don't have sodium cyanide for our cadmium solution. As procurement takes ages, we were wondering if we could substitute sodium cyanide with zinc cyanide as we have an abundance of the stuff. Any advice is welcome.

F.J. Visagie
- Cape Town, South Africa
June 25, 2024

A. Hi F.J.,
Sorry but I can't imagine that working. Still, your inquiry is on line if anyone can offer encouragement
Luck & Regards,

ted_yosem
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. Hello F.J.
When you add sodium cyanide you are adding 'free cyanide'.
it will attach to the cadmium metal allowing it to remain soluble in the hydroxide matrix. additionally there is an excess of cyanide in order to allow cadmium to dissolve into solution from the anodes.

Zinc cyanide acts like the cadmium and it too has cyanide ligands attached to it in this solution, so it does not add to the overall 'free cyanide' content. The sodium is just present as a carrier ion and does not co-ordinate strongly with the cyanide. that is why it is added to the solution. Also, the zinc may also plate along with the cadmium onto your components changing the characteristics of the coating.

Mark Lees
- A dull grey rock in the Irish Sea

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